title: Single-chain variable fragment albumin fusions bind the neonatal Fc receptor (FcRn) in a species-dependent manner: implications for in vivo half-life evaluation of albumin fusion therapeutics.
abstract: Albumin has a serum half-life of 3 weeks in humans. This has been utilized to extend the serum persistence of biopharmaceuticals that are fused to albumin. In light of the fact that the neonatal Fc receptor (FcRn) is a key regulator of albumin homeostasis, it is crucial to address how fusion of therapeutics to albumin impacts binding to FcRn. Here, we report on a detailed molecular investigation on how genetic fusion of a short peptide or an single-chain variable fragment (scFv) fragment to human serum albumin (HSA) influences pH-dependent binding to FcRn from mouse, rat, monkey, and human. We have found that fusion to the N- or C-terminal end of HSA only slightly reduces receptor binding, where the most noticeable effect is seen after fusion to the C-terminal end. Furthermore, in contrast to the observed strong binding to human and monkey FcRn, HSA and all HSA fusions bound very poorly to mouse and rat versions of the receptor. Thus, we demonstrate that conventional rodents are limited as preclinical models for analysis of serum half-life of HSA-based biopharmaceuticals. This finding is explained by cross-species differences mainly found within domain III (DIII) of albumin. Our data demonstrate that although fusion, particularly to the C-terminal end, may slightly reduce the affinity for FcRn, HSA is versatile as a carrier of biopharmaceuticals.
authors.affiliation: Centre for Immune Regulation (CIR) and Department of Biosciences, University of Oslo, N-0316 Oslo, Norway. j.t.andersen@imbv.uio.no
authors.forename: Jan Terje
authors.initials: JT
authors.lastname: Andersen
authors.forename: Jason
authors.initials: J
authors.lastname: Cameron
authors.forename: Andrew
authors.initials: A
authors.lastname: Plumridge
authors.forename: Leslie
authors.initials: L
authors.lastname: Evans
authors.forename: Darrell
authors.initials: D
authors.lastname: Sleep
authors.forename: Inger
authors.initials: I
authors.lastname: Sandlie
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D006207:Half-Life; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D051379:Mice; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D011961:Receptors, Fc / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism* / Q000627:therapeutic use*; D012709:Serum Albumin / Q000378:metabolism* / Q000627:therapeutic use*; D057127:Single-Chain Antibodies / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D015395:Histocompatibility Antigens Class I; D050505:Mutant Proteins; D011961:Receptors, Fc; D011993:Recombinant Fusion Proteins; D012709:Serum Albumin; D057127:Single-Chain Antibodies; C100688:Fc receptor, neonatal
keywords: Albumin; Animal Models; Antibody Engineering; Bioengineering; Drug Delivery; Pharmacokinetics; Receptor Recycling; pH Regulation